1. Field of the Invention
The present invention relates to an image reading and recording apparatus, such as an electronic blackboard, a facsimile machine etc., for optically reading information written on a board or a flexible sheet and regenerating the information in the form of a hard copy. The invention is also concerned with an image recording unit for used in the image reading and recording apparatus.
2. Description of the Prior Art
A known electronic blackboard includes, as shown in FIGS. 5 and 6, a board 1 for receiving information written thereon, a reading unit 2 movable along the board 1 for reading the information on the board, a guide rail 3 for movably supporting the reading unit 2, a pair of wheels 4 and 4 (FIG. 6) attached to the reading unit 2 for rolling movement along the guide rail 3, an endless wire rope 5 extending along the guide rail 3, a pair of pulleys 6 and 7 around which the wire rope 5 is trained, a motor 8 attached to the guide rail 3 for driving the pulley 6. The reading unit 2 is firmly connected to a portion of the wire rope 5 so that when the wire rope 5 is moved around the pulleys 6 and 7, the reading unit 2 moves along a surface of the board 1 to read information written thereon.
According to another known electronic blackboard, such as shown in Japanese Patent Laid-open Publication Nos. 62-185453, 63-194998 and 63-276360, the drive motor is attached to the reading unit instead of the guide rail. The drive motor rotates a drive roller which is held in friction contact with a guide rail. Thus, upon rotation of the drive roller, the drive roller rolls along the guide rail to move the reading unit along the guide rail during which time information written on a board is read by the reading unit.
Both of the foregoing known electronic blackboards are, however, not satisfactory due to the drawbacks described below.
In the first-mentioned known electronic blackboard using the wire rope such as shown in FIGS. 5 and 6, the pair of pulleys 6 and 7 and the drive motor 8 must be disposed outside the range of movement of the reading unit 2 and, therefore, a long guide rail 3 is needed. In addition, the drive motor 8 is disposed behind the guide rail 3 so that the overall depth of the electronic blackboard is relatively large.
The second-mentioned known electronic blackboard is free from the foregoing problem because the drive motor and the drive roller are mounted on the reading unit. However, since a driving force tending to move the reading unit is given solely by a frictional force acting between the drive roller and the guide rail, the movement of the reading unit tends to become unstable due to slippage between the driving roller and the guide rail. As a result, the reading unit cannot read the information on the board with a sufficient degree of reliability and accuracy.
On the other hand, a conventional image recording unit which may be incorporated in an electronic blackboard or a facsimile machine includes, as shown in FIGS. 7 and 8, a recording head 9 for printing information on a recording paper 10 and a drive unit 11. The drive unit 11 is composed of a motor 12, an intermediate gear 13 meshing with a pinion 14 mounted on a drive shaft 12a of the motor 12, and a transmission gear 15 meshing with the intermediate gear 13. The recording head 9 and the drive unit 11 are mounted on a body (not shown) of the image recording unit. The image recording unit also includes a recording roller 16 for feeding the recording paper 10 while forcing the recording paper 10 against the recording head 9. The recording roller 16 has a driven gear 17 and is attached to a lid assembly (not shown) which is pivoted to the body of the image recording unit and movable between an open position and a closed position relative to the unit body. When the lid assembly is moved from the open position to the closed position, the driven gear 17 is brought into meshing engagement with the transmission gear 15 and, at the same time, the recording roller 16 forces the recording paper 10 against the recording head 9. Conversely, when the lid assembly is moved from the closed position to the open position, the recording roller 16 and the driven gear 17 move in the direction indicated by the arrow A shown in FIG. 8. The transmission gear 15 is disposed on the same side as the recording head 9 relative to the recording roller 16.
With this construction, when the motor 12 is driven to rotate transmission gear 15 in the direction of the arrow B, the driven gear 17 is rotated by the transmission gear 14 in the direction of the arrow C. In this instance, the driven gear 17 is subjected to a force tending to move the driven gear 16 and the recording roller 16 in the direction of the arrow A (FIG. 8), thereby urging the lid assembly toward its open position. The recording roller 16 is no longer possible to force the recording paper 10 reliably against the recording head 9. Under these circumstances, the printing quality is significantly deteriorated and sometimes the printing itself becomes impossible.